1. Field of the Invention
The present invention relates to a light-emitting device, and more particularly to an integrally formed high-efficient multi-layer light-emitting device, in which the brightness and the evenness of the light output will be improved, and the amounts of the phosphor and silicone used are reduced.
2. The Prior Arts
The light-emitting theory of LED takes advantage of the intrinsic properties of semiconductors, which is different from the theory of electric discharging, heat and light-emitting of an incandescent light tube. Because light is emitted when electric current forward flowed across the PN junction of a semiconductor, the LED is also called cold light. The LED has the features of high durability, long service life, light weight, low power consumption, and being free of toxic substances like mercury, and thereby it can be widely used in the industry of the light-emitting device, and the LEDs are often arranged in an array and often used in such as electric bulletin board or traffic sign.
Conventionally, a phosphor layer is formed on the light-emitting surface. Usually, a solution containing the phosphor is filled, coated, or dropped on the light-emitting surface. The phosphor layer is capable of absorbing at least a portion of the first color light emitted by the light-emitting dies, and subsequently emitting a second color light, and the first color light and the second color light will be mixed together in the phosphor layer to produce the desired color light.
FIG. 1 is a cross-sectional view showing a package structure of an array type multi-layer LED according to the prior art. Referring to FIG. 1, the array type multi-layer LED package structure includes a substrate 10a, a plurality of LED dies 18a, a package module 12a, a lead frame 14a, and a mask 16a, wherein the substrate 10a was disposed on the bottom of the package structure, and the package module 12a was used for encapsulating the substrate 10a and the lead frame 14a. The LED dies 18a were arranged in an array on the substrate 10a. The substrate 10a is made of metal. The LED dies 18a and the lead frame 14a were electrically connected with each other. The mask 16a covered the package module 12a. An insulating protection layer 20a covered the LED dies 18a. A phosphor layer 22a was formed on the insulating protection layer 20a. 
However, in order to increase the brightness of the conventional LED package structure, enough space should be left for disposing a plurality of LED dies in the package module 12a. The large amounts of the phosphor and silicone are required to form the phosphor layer 22a and the insulating protection layer 20a for covering the LED dies 18a, and thereby the material cost is greatly increased. Furthermore, the LED dies 18a are often arranged in an array, and thereby the light emitted by the LED dies 18a arranged in different rows will hit the inner sidewall of the package module 12a at different angles so that the reflected light will cross over each other, and thereby the evenness of the light output will be poor. Accordingly, it is desirable to provide an integrally formed high-efficient multi-layer light-emitting device capable of solving the problems existing in the conventional LED package structure.